The advent of the jet age toward the end of World War II brought a new challenge to aircraft modelers--how to simulate jet-powered flight. One early solution included mounting a glow-plug engine in the nose of the model and using a tractor propeller to pull the model through the air. The spinning propeller is invisible in flight and such models perform rather well. Another approach is to use a real "miniaturized" jet engine. However, such engines are generally too difficult for radio-control pilots to manage, as the engines cannot be throttled, are excessively noisy, and create a fire hazard.
By far the most successful approach is to power the model aircraft with a ducted fan driven by a high-speed engine. The engine turns a multi-bladed fan mounted inside a circular housing (the duct), and the fan unit produces thrust which pushes the model through the air. With a ducted fan the entire power plant can be hidden inside most models, thus allowing for the building of realistic replicas of jet aircraft. Further, ducted-fan models have many of the flight characteristics of full-size jet aircraft, offering new challenges to radio-control pilots. An excellent source of background material on ducted-fan aircraft is Building & Flying Ducted-fan RC Aircraft, by Dick Sarpolus, published in 1981 by Kalmback Publishing Co.
Almost all important jet powered aircraft have been successfully modeled using ducted-fan systems. The notable exception are aircraft with vertical take-off and landing (VTOL) capability, such as the well-recognized British Harrier "jump" jet. The difficulties in achieving hover to horizontal flight have, for the most part, stymied the developers of lightweight remotely controlled aircraft, and only recently was the chasm from vertical to horizontal flight and back successfully traversed. See R/C VTOL Makes History, by John A. Gorham, published in the October 1993 issue of Model Airplane News. However, the VTOL radio-controlled aircraft which first successfully navigated transitory flight looks and behaves a far cry from the sleek and stylish Harrier. The Grumman Electronics Systems' 1/3-scale R/C model of a proposed VTOL aircraft utilized twin rotatable, externally mounted ducted-fan engine and fan combinations employing a vane-control system manipulated by flight-control servos. Though conquering transitory flight, the Grumman project did not provide aircraft modelers with a workable R/C power plant for internal mounting in made-to-scale fighter aircraft models.